Field
The present invention relates generally to wireless power. More specifically, the present invention relates to methods and devices for communication within a wireless power system.
Background
Approaches are being developed that use over the air power transmission between a transmitter and the device to be charged. These generally fall into two categories. One is based on the coupling of plane wave radiation (also called far-field radiation) between a transmit antenna and receive antenna on the device to be charged which collects the radiated power and rectifies it for charging the battery. Antennas are generally of resonant length in order to improve the coupling efficiency. This approach suffers from the fact that the power coupling falls off quickly with distance between the antennas. So charging over reasonable distances (e.g., >1-2 m) becomes difficult. Additionally, since the system radiates plane waves, unintentional radiation can interfere with other systems if not properly controlled through filtering.
Other approaches are based on inductive coupling between a transmit antenna embedded, for example, in a “charging” mat or surface and a receive antenna plus a rectifying circuit embedded in the host device to be charged. This approach has the disadvantage that the spacing between transmit and receive antennas must be very close (e.g. mms). Though this approach does have the capability to simultaneously charge multiple devices in the same area, this area is typically small, hence the user must locate the devices to a specific area.
In a wireless power system, it may be beneficial for communication between devices to achieve power control for improved system efficiency. For example only, communication may assist in near-field communication (NFC) device detection, rogue receiver detection, and rectifier voltage control. Further, to be compliant with FCC Part 18 regulations, forward link communication in a wireless power system is not allowed, and all reverse links must be passive in terms of load modulation.
Additionally, in order to achieve charge port concurrent continuous charging for multiple devices (e.g., mobile telephones), communication must not interrupt the charging and, therefore, charging and communication should happen concurrently. Moreover, each chargeable devices needs to sync with each other to avoid collision, as there is no forward link to sync the receivers.
A need exists for methods, systems, and devices for enhancing communication between devices within a wireless power system.